Spring structure for producing small displacements

ABSTRACT

The polygonal mirror of a light beam scanner is aligned on a shaft by three mounting fixtures, each comprising a stiff spring bearing against one side of the mirror and a relatively soft spring bearing against the opposite side. The soft spring is compressed against the mirror by a bolt. The rotational plane of the mirror is adjusted by threading the bolts toward or away from the mirror.

Inventors H r'bcinawly; Leif Rongved, Summit; John W. Stallord.

East Orange; John W. West, Mlllington, all of NJ.

Appl. No. 830,393

Filed June 4. 1969 Patented Nov. 23, 1971 Assignee Bell Telephone Laboratories. Incorporated Murray Hill. Berkeley Heights, NJ.

SPRING STRUCTURE FOR PRODUCING SMALL DISPLACEMENTS 4 Claims, 5 Drawing Figs.

US. Cl 350/6 Int. Cl e G02!) l7/00 Field of Search 350/6, 7, 299. 310, 28; 248/350. 9, 358. 483. 487; I78/7.6; 74/55; 267/137 T369613 United .eierences Cited UNITED STATES PATENTS 2,7] 1,297 6/1955 Thiele t. 248/358 3,079,803 3/!963 Moller 74/55 3.1 l3,755 l2/l963 Stevens et al.. 248/358 3,476.34) I 1/1969 Smith 248/476 3.478.608 ll/l969 Met 350/3 l0 X Primary Examiner- David Schonberg Assistant Exammen-Michael J. Tokar Auorneys- R. J Guenther and Arthur J. Torsiglieri ABSTRACT: The olygonal mirror of a light beam scanner is aligned on a shaft by ee mounting fixtures. each comprising a stiff spring hearing against one side of the mirror and a relatively soft spring hearing against the opposite side. The soft spring is compressed against the mirror by a bolt. The rotational plane of the mirror is adjusted by threading the bolts toward or away from the mirror.

PAIENTEDNHY 23 3.622.221

SHEET 1 or 2 j llb J. W. STAFFORD V J. W. WEST ATTORA/FY SPRING STRUCTURE FOR PRODUCING SMALL DISPLACEMENTS BACKGROUND OF THE INVENTION This invention relates to apparatus for placements. and more particularly. rotational member on a central axis.

The copending application of D. R. Herriott-K. M. PooleA. Zacharias. Ser. No. 796.456. filed Feb. 4. 1969. assigned to Bell Telephone Laboratories. Incorporated, describes light beam scanning apparatus employing a rotating producing small disto apparatus for aligning a by an electrical motor. a relatively gross device, the application shows how, by proper light beam coding. highly precise photographic reproduction can be obtained. A cursory examination of the apparatus demonstrates the desirability of ac- SUMMARY OF THE INVENTION It is an object of this invention to provide a mechanical deamplifier which permits a relatively large manually applied displacement to be translated to a very small displacement precisely related to the large one.

It is a specific object of this invention to for accurately aligning a polygonal mirror central axis of rotation. M

These and other objects of the invention are attained in an illustrative embodiment thereof comprising a rotatable polygonal mirror held in place by three mounting fixtures each provide apparatus with respect to a much larger spring constant than the soft spring.

The friction due to the compression of the polygonal mirror between the two springs of each mounting fixture holds the negligible drift during use. It can be shown that. in both theory and in practice, alignment by the spring structures described mechanical leverage deamplification.

These and other objects. features. and advantages of the invention will be better understood from a consideration of the following detailed description taken in conjunction wit the accompanying drawing.

DRAWING DESCRIPTION polygonal mirror and associated partly in section. of the mirror and ap- 2 DETAILED DESCRIPTION mounting fixtures 14.

a support plate 17, on the axle 12 by a nut 18.

each mounting fixture comprises a coil which in turn is mounted Referring to FIG. 2.

includes three projections or pads 25. each located on a central axis of a corresponding coil spring 20(only one of the three pads 25 is shown in FIG. 2). The coil spnng 20 is stabilized by a diaphragm 26.

mounted symmetrically with respect to axis 13 to form a continuous annular gap 29 between the mirror and the axle.

Each projection 25 indenting into the mirror constitutes a spring which is extremely stiff by comparison to the coil spring by adjustment of one of the mounting fixaxis defined by the other two fixtures. For example. if the spring head 27 of mounting fixture 14 produces K t 62 K 1 52 where K, is the spring constant of spring 200 and K, is the spring constant of spring 254. It can be appreciated that if K, is many orders of magnitude larger than K,. then 6, is many order of magnitude smaller than 6,.

One can see intuitively from FIG. So that if there is not substantial friction in the axial direction, that is. in the direction member Ila is spuriously deflected. it will soon return to its precise equilibrium position; that is. there will be little or no hysteresis.

many orders of magnitude of the corresponding spring 20. The mounting apparatus is designed such that each mounting fixture exerts 57 pounds of force on the mirror and an FIG. 3b shows an alternative form in which spring 25b is designed to take tension rather than compression. Mechanical deamplification occurs according to equation l) where K, is the spring constant of spring 20b and K is the spring constant of spring 25b. As spring 20b is compressed, spring 25b is tensed, rather than compressed as in H0. 3a.

The structure of FIGS. 1

compressive friction over only a short distance; when the pin is in the dotted position 3]. it is axially withdrawn with little friction.

The apparatus specifically shown and described is intended to be only illustrative ofthe principles involved. Various other embodiments and modifications may be made by those skilled in the art without departing from the spirit and scope of the invention.

What is claimed is:

l. A precisely adjustable mirror mount assembly comprismg:

a first member having a central aperture and first and second opposite walls: the second member extending through the aperture; said second member comprising a wall portion partially coextensive with the second wall ofthe first member;

means for aligning the first member with respect to the second member comprising a plurality of mounting fixtures:

each mounting fixture comprising a spring and a bolt for axially compressing the spring against the first wall of the first member;

projections from the wall portions of the second member, each contacting the second wall of the first member at a the axis of a spring, whereby the first member is compressed between corresponding springs and projections;

each bolt being threaded to a threaded member rigidly coupled to the second member;

the axial resiliency of the projections being much smaller than the axial resiliency of the springs, whereby a relative ly large displacement of the spring gives a small displacement ofthe first member. 2. The com brnatron of claim I wherein:

the aligning means comprises first, second. and third mounting fixtures, whereby adjustment of the first mounting fixture causes the first member to rotate on an axis defined by the second and third fixtures.

3. The combination of claim 1 wherein:

the aperture and the second member are cylindrical. the aperture having a larger diameter than that of the second member;

means for temporarily displacing the first member from the second member comprising a plurality of pins adapted to be inserted in the aperture between the first and second members;

the mounting fixtures being adapted to provide sufficient friction to support independently the first member;

the pins being adapted to be removed after the mounting fixtures have provided sufficient friction to support the first member.

precision a small displacement ofa mirror member relative to a support comprising:

three pairs of springs; each pair of springs being displaced from the other pairs and each including a first spring having one end bearing the mirror member and a second spring coaxial with the first spring having one end bearing against the side of the mirror member diametrically opposite the first spring and having another end bearing against the support;

said first and second springs being designed to provide a spring bias against compression;

said first and second springs and the mirror member being free to move axially substantially without friction;

the second spring having a substantially larger spring constant K than the spring constant K, ofthe first spring; and

' the support each of said 6, relative to the support to compress said first and second springs, thereby to displace the mirror member by an amount 8, relative to the support, where 6 is substantially given by Patent No.

Inventor(s) Gunter J. W. Kossyk, Leif Rongved, John W. Stafford, John W. west Dated November g, 1971 C01. 1, line 001. 2, line line line

line

001. A, line (SEAL) A L; to s B:

EDWARD I LFLETCI-IERJR. Attesting Officer It is certified that error appears in the above-identified patent and that said Letters Patent arehereby corrected as shown below:

change "maybe" to --may be--;

in the equation change "5 second occurrence,

1 change "not" to ---no--.

change 2 second occurrence, to --6 Signed and sealed this 30th day of May 1972.

ROBERT GOTTSCHALK Commissioner of Patents 

1. A precisely adjustable mirror mount assembly comprising: a first member having a central aperture and first and second opposite walls; the second member extending through the aperture; said second member comprising a wall portion partially coextensive with the second wall of the first member; means for aligning the first member with respect to the second member comprising a plurality of mounting fixtures; each mounting fixture comprising a spring and a bolt for axially compressing the spring against the first wall of the first member; projections from the wall portions of the second member, each contacting the second wall of the first member at a point substantially on the axis of a spring, whereby the first member is compressed between corresponding springs and projections; each bolt being threaded to a threaded member rigidly coupled to the second member; the axial resiliency of the projections being much smaller than the axial resiliency of the springs, whereby a relatively large displacement of the spring gives a small displacement of the first member.
 2. The combination of claim 1 wherein: the aligning means comprises first, second, and third mounting fixtures, whereby adjustment of the first mounting fixture causes the first member to rotate on an axis defined by the second and third fixtures.
 3. The combination of claim 1 wherein: the aperture and the second member are cylindrical, the aperture having a larger diameter than that of the second member; means for temporarily displacing the first member from the second member comprising a plurality of pins adapted to be inserted in the aperture between the first and second members; the mounting fixtures being adapted to provide sufficient friction to support independently the first member; the pins being adapted to be removed after the mounting fixtures have provided sufficient friction to support the first member.
 4. Apparatus for producing with precision a small displacement of a mirror member relative to a support comprising: three pairs of springs; each pair of springs being displaced from the other pairs and each including a first spring having one end bearing against one side of the mirror member and a second spring coaxial with the first spring having one end bearing against the side of the mirror member diametrically opposite the first spring and having another end bearing against the support; said first and second springs being designed to provide a spring bias against compression; said first and second springs and the mirror member being free to move axially substantially without friction; the second spring having a substantially larger spring constant K2 than the spring constant K1 of the first spring; and three members in engagement with the support, each of said members being capable of axially moving an end of one of said first springs toward the mirror member by an amount delta 1 relative to the support to compress said first and second springs, thereby to displace the mirror member by an amount delta 2 relative to the support, where delta 2 is substantially given by 